Many of the current generation of foggers used for spraying or dispersing pesticides, defoliants, fungicides and other chemicals are known as ultra low volume (ULV) cold aerosol generators or fog generators. Such devices normally include a prime mover, a blower unit, a nozzle assembly, and a supply tank for the chemical as well as a suitable control means. The chemical is normally fed into the nozzle assembly where it is entrained in the air stream flowing therethrough and dispersed into the atmosphere. The generators are also normally self-contained units and are removably mounted in or on a vehicle, utilizing, for example, skids or similar platforms.
One common use is to mount the generator on a truck or similar vehicle for use in spraying pesticides in residential areas. As such, the generator must be shut down and the supply disconnected when the vehicle stops at stop lights, stop signs, etc. since the concentrated pesticide can be detrimental to humans, automobile finishes, etc. Regulations governing the use of and dispersion of the pesticides or other chemicals propagated by the Environmental Protection Agency and many municipal and state governmental agencies require that the spray be completely stopped in a matter of seconds upon stopping the vehicle.
Prior art generators are, in general, able to cut off the spray; however, a complete stoppage has taken several minutes as the normal procedure is to leave the blower and motor on while cutting off the fluid supply, since restarting the motor requires that the operator get out of the vehicle and pull the starter rope on the motor. The vacuum created by the still-operating blower draws the fluid out of the supply line and, in some cases, out of the supply tank resulting in a continuous, albeit reduced, spray being emitted. Thus, there is a definite concern which, prior to the present invention, has not been addressed.